1. Field of the Invention
The present invention relates to a wiper blade assembly, particularly of the type used for mounting windscreen wipers on motor vehicles.
2. Description of the Prior Art
A conventional wiper blade assembly comprises a primary yoke for attachment to a wiper arm and two secondary yokes pivotally attached to opposite ends of the primary yoke. In the case of a dual wiper blade assembly, two side-by-side secondary yokes may optionally be attached to each end of the primary yoke. A separate tertiary yoke is articulated to one, usually the outermost one, of the two free ends of each secondary yoke. Claws for mounting a single wipe blade or dual, parallel wiper blades are provided at the ends of the tertiary yokes not occupied by the tertiary yokes. There is thus provided a flexible six point mounting for the or each wiper blade, which affords a reasonable degree of contact between the wiper blade and the windscreen, at least in calm conditions when the vehicle is travelling slowly.
A problem arises with such a wiper blade assembly, however, when the vehicle is travelling forwards, particularly at high speed. The upward air flow over the windscreen tends to lift the wiper blade assembly away from the windscreen particularly on its downward stroke. To alleviate this problem, spoilers or wind deflecting vanes have been proposed for the leading edge of the assembly. However, the attachment of such spoilers to the primary yoke complicates the manufacture of the assembly.